Southern part of Sumatra is known for its high deliverability hydrocarbon gas formation with flow rate up to 200 MMSCFD produced from a single well. The fractured network present mainly in its granite basement formation posed as the primary hydrocarbon contributor aside to the carbonate zone. High formation pressure with massive gas reservoir as its driving mechanism combined with total loss circulation due to geological fault in the same section, lead to operation with various hazard combined which demands potent solution. Advanced technologies required to execute the operation in safest and efficient manner.
Downhole Casing Valve (DCV) is one of Managed Pressure Drilling (MPD) equipment used to support operation with deep and high-pressure formation, installed alongside with casing to provide sealing of the well at depth. Equipped with flapper type valve and full borehole size, DCV which is surface controlled, enables operator to seal the well in the absence of any string. The seal created by DCV allows the string to be pulled out preventing to kill a live well.
The South Sumatra blocks depicts enormous potential gas reservoir. Located in the fault of basement where total loss circulation will occur in highest probable manner. Utilization of chemical mixed mud was impractical considering the total loss circulation. Thus, pressure exerted from fluid column and pumping flow rate from string needs to be compensated by surface backpressure. In addition, to accommodate deep footage penetration of the section, hard basement formation, complex completion running sequence, and multiple tripping for BHA changes, requirement of DCV shifted from nice-to-have into a must-have segment. Without the need of killing the well nor changing the mud system, DCV allows tripping operation to be completed safely and efficiently by sealing the well with its flapper, saving costs and time on each tripping operation. DCV utilization successfully supports drilling high-pressure gas reservoir through basement fault until target depth reached safely and efficiently.